Electric machines, such as alternating current electric generators, or alternators are well known. Prior art alternators typically include a stator assembly and a rotor assembly disposed in an alternator housing. The stator assembly is mounted to the housing and includes a generally cylindrically-shaped stator core having a plurality of slots formed therein. The rotor assembly includes a rotor attached to a generally cylindrical shaft that is rotatably mounted in the housing and is coaxial with the stator assembly. The stator assembly includes a plurality of wires wound thereon, forming windings. The stator windings are formed of slot segments that are located in the core slots and end loop segments that connect two adjacent slot segments of each phase and are formed in a predetermined multi-phase (e.g. three or six) winding pattern in the slots of the stator core.
The rotor assembly can be any type of rotor assembly, such as a “claw-pole” rotor assembly, which typically includes opposed poles as part of claw fingers that are positioned around an electrically charged rotor coil. The electric current in the rotor coil produces a magnetic field in the claw fingers. As a prime mover, such as a steam turbine, a gas turbine, or a drive belt from an automotive internal combustion engine, rotates the rotor assembly, the magnetic field of the rotor assembly passes through the stator windings, inducing alternating electrical currents in the stator windings in a well known manner. The alternating electrical currents are then routed from the alternator to a distribution system for consumption by electrical devices or, in the case of an automotive alternator, to a rectifier and then to an automobile battery.
One type of device is a high slot fill stator, which is characterized by rectangular shaped conductors whose width, including any insulation fit closely to the width, including any insulation of the rectangular shaped core slots. High slot fill stators are advantageous because they are efficient and help produce more electrical power per winding than other types of prior art stators.
One disadvantage of a six phase high slot fill stator is that it requires six diode pairs (one for each phase). This increases the cost of the stator due to the high cost of the diode pairs. A machine having three diode pairs has been developed having a three phase winding wherein each phase is comprised of two conductors, one being shifter thirty electrical degrees with respect to the other. This solution have fewer diode pairs, but requires an additional reverse connection between the two conductors, thereby increasing cost as well as manufacturing complexity. Furthermore, this solution does not address the issue of the standard six pitch winding having high resistance due to the length of the conductor in each six pitch end loop segment. A conductor with reduced end loop length results in higher output, higher efficiency, lower stator temperatures, and lower cost.
Accordingly, there is a need for a stator winding that reduces the number of diode pairs, does not require any extra reverse connections, and reduces the length of the end loop segments, and therefore the electrical resistance.